Subject: [PATCH] vhost: clean up outstanding buffers before setting vring

From: Shirley Ma <[email-masked]>
Date: Tue, 19 Jul 2011 11:02:26 -0700

The outstanding DMA buffers need to be clean up before setting vring in
vhost. Otherwise the vring would be out of sync.

Signed-off-by: Shirley Ma<[email-masked]>
---

 drivers/vhost/vhost.c |   11 +++++++++--
 1 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index c14c42b..d6315b4 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -445,8 +445,10 @@ void vhost_dev_cleanup(struct vhost_dev *dev)
 			vhost_poll_flush(&dev->vqs[i].poll);
 		}
 		/* Wait for all lower device DMAs done. */
-		if (dev->vqs[i].ubufs)
+		if (dev->vqs[i].ubufs) {
 			vhost_ubuf_put_and_wait(dev->vqs[i].ubufs);
+			kfree(dev->vqs[i].ubufs);
+		}
 
 		/* Signal guest as appropriate. */
 		vhost_zerocopy_signal_used(&dev->vqs[i]);
@@ -651,6 +653,12 @@ static long vhost_set_vring(struct vhost_dev *d, int ioctl, void __user *argp)
 	vq = d->vqs + idx;
 
 	mutex_lock(&vq->mutex);
+	/* Wait for all lower device DMAs done. */
+	if (vq->ubufs)
+		vhost_ubuf_put_and_wait(vq->ubufs);
+
+	/* Signal guest as appropriate. */
+	vhost_zerocopy_signal_used(vq);
 
 	switch (ioctl) {
 	case VHOST_SET_VRING_NUM:
@@ -1592,7 +1600,6 @@ void vhost_ubuf_put_and_wait(struct vhost_ubuf_ref *ubufs)
 {
 	kref_put(&ubufs->kref, vhost_zerocopy_done_signal);
 	wait_event(ubufs->wait, !atomic_read(&ubufs->kref.refcount));
-	kfree(ubufs);
 }
 
 void vhost_zerocopy_callback(void *arg)